The present invention relates generally to imaging systems and more particularly to a method to improve the display of temporal changes. Imaging devices, such as x-ray machines, are widely used in both medical and industrial applications. Imaging devices often use temporal processing to track change in an object over time.
Temporal processing systems typically include the following general modules: acquisition storage module, segmentation module, registration module, comparison module, and reporting module. The input images are 1-D, 2-D, 3-D, derived, synthesized, or montaged, where multiple separate images from a single time point are combined to provide a larger composite, seamless image.
Detection of change in medical images of a patient, which are acquired at two different instances in time, has great potential for improving diagnosis. The advent of digital imaging allows computer-assisted detection and identification of these changes and the creation of a “dissimilarity image” containing the change information. This dissimilarity image can be read by a human controller or can become the input to an automated analysis device such as a CAD (computer assisted diagnosis) algorithm.
Currently, as part of Mitsubishi Space Software's “temporal subtraction” application, dissimilarity images are calculated using a simple pixel-by-pixel subtraction of registered images. Simple subtraction, however, results in images with poor contrast, and is not substantially robust when the two initial images are acquired using different techniques.
For a temporal subtraction image, the resulting pixel values (and hence the displayed gray-levels) are proportional to the difference or dissimilarity in pixel value between two input images acquired with temporal separation.
Input images are often registered and processed to compensate for several factors such as: the difference in positioning of the subject during the two image the difference in acquisition parameters, the difference in the bit resolution of the images, and the differences in any pre or post processing that may have been applied to the images.
Image comparison is a common task in a number of applications including temporal processing of mono-modality images (1-D, 2-D, 3-D, derived, synthesized, montaged). Current methods involve simple arithmetic operations conducted on these images, including subtraction or addition, which are non-adaptive in terms of the spatial image content. Therefore, there is a need to improve the comparison module with more sophisticated methods, which are adaptive and which provide better results for subsequent processing and display techniques.
The disadvantages associated with current, imaging systems have made it apparent that a new technique for temporal processing is needed. The new technique should substantially increase accuracy of information acquired obtained from temporal processing. The present invention is directed to this end.